If a bride says she's feeling short of breath before heading into the ceremony, nerves are usually to blame. But for 21-year-old bride Kirstie Mills Tancock, there was a deeper cause at play. Tancock was born with cystic fibrosis, an inherited chronic disease that clogs the lungs and affects the digestive system, confining her to a wheelchair with IV support during the four months last year she spent planning her wedding and waiting for a lung transplant. TLC captured Tancock's race toward the altar for a new documentary called "Breathless Bride: Dying to Live," premiering Feb. 29 at 10 p.m. EST.

Days after her June 16 wedding to Stuart Tancock, 27, the bride underwent a double lung transplant at a hospital in London. "Kirstie is a complete fighter," her now-husband says in the documentary. "You can't put her down. She'll fight for anything." The CF Patient Registry lists that 90 percent of people with the disease who received lung transplants lived for one year after transplantation, and half are still living after five years. Of the 30,000 people in the United States with the disease, most can expect to live into their 30s and 40s.

So for however long they have together, Stuart says he and Kirstie are going to make it count. "In life, you don't know who you will fall in love with," he says. "But I would rather something short, and be as happy as we can be, than a lifetime of just going through the motions."